1. Field of the Invention
The present invention relates to a storage medium having a game program stored thereon and a game apparatus, and more particularly to a storage medium having stored thereon a game program and a game apparatus which execute a game in which an object representing a target is shot in a virtual three-dimensional space.
2. Description of the Background Art
Conventionally, well-known is a game apparatus which executes a game in which a target object representing a target is shot in a virtual three-dimensional space. The game apparatus has a contact determination area defined for each of the target object, and a bullet object shot from a gun and the like, so as to determine whether or not a bullet hits a target. Specifically, whether or not the bullet has hit the target is determined depending on whether or not the target object contacts the bullet object. In general, the size and the shape of the contact determination area of each of the target object and the bullet object do not change in accordance with a game state. Accordingly, while the target object is moved, the contact determination area of the target object is also moved in accordance with the target object, and therefore it is difficult that a bullet hits a moving target, and it is likely to be too difficult for a player to play the game.
Patent Document 1 (Japanese Laid-Open Patent Publication No. 2005-246071) discloses a method for reducing the difficulty with which a bullet hits a moving target. The image generation system disclosed in Patent Document 1 determines whether or not a target object is moving, and when the target object is determined to be moving, the contact determination area of the target object is increased. Thus, the contact determination area of the bullet object more readily contacts the contact determination area of the target object, and therefore the bullet can more easily hit the moving target, thereby reducing the difficulty.
However, the image generation system disclosed in Patent Document 1 needs to determine whether or not all the target objects appearing in the three-dimensional space is moving so as to define, based on the determination result, the contact determination area. Accordingly, the image generation system has a problem that a processing load of the system changes depending on the number of the target objects appearing in the three-dimensional space, and the increased number of the target objects leads to an increase in processing load of the system.